Is it possible that I don't have the /dev/hda3 Sunlable partition setup correctly?

I'd say its possible...

I had a hell of a time with a pair of 40GB ATA133 drives I was trying to use in my U10, I never managed to get the sun disk setup to work properly, I would suggest you start the solaris install, let that sort the disk setup out, and then reboot and start the Gentoo install (without removing the 3rd partition).

Hope that helps._________________Toady

Gentoo Laptop
3.1.10-gentoo-r1, Intel Core 2 Duo (32bit)
Gnome on the desk, Intel in the box, on-board everything, but it all works!